In the case of a footwear item, in order to ensure the hold on the leg while preventing the item from rolling, the retaining edge is usually made by a rib trimming in a double knit layer, of which the dimensions and texture vary according to the features of construction and thickness of the tubular part of the item. This technique is illustrated for knee-high stockings in document FR 2 946 668.
It is known, for example by documents GB 1 427 777, EP 0 034 981 or FR 2 819 827, to produce a pair of tights by knitting two tubes on a circular knitting machine, by opening the top of each tube along a substantially vertical seaming and by assembling by confection the two tubes at the edges of said seamings in such a manner as to form the panty part of the pair of tights. The waistband part of the pair of tights may be formed by sewing an added waistband strip or more traditionally by a double knit layer obtained during the knitting itself and of which the dimensions and texture vary according to the features of construction and thickness of the part below the waistband. This double thickness may be obtained by knitting a welt which is fastened by knitting to the tube of the item, according to what is called “hanging plate”; this double layer part visually offers a rather significant demarcation with the rest of the outline, which may even be visible beneath clothes. With the purpose of reducing this traditional double layer, it has been proposed in document FR 2 942 109 a fine elastic knitted lingerie item, having an elastic retaining edge, comprising a fine elastic knit layer and a strip of elastic material thermally bonded on said fine elastic knit layer, this elastic material being also advantageously knitted in fine knit. Although this item is very popular, it requires an additional thermal bonding operation in the production of the pair of tights.
It would be desirable to propose items with a single thickness waistband without demarcation, obtained directly by knitting on a circular knitting machine.
However, in practice it is difficult to obtain a satisfactory retaining edge by knitting such an item on a circular knitting machine. For technical reasons, the first knitted courses cannot be knitted on all the needles, as opposed to the “normal” courses of the basic tubular item; for example first they are knitted 1 needle out of 4, then 1 needle out of 2; hence, in these first courses there is less length of absorbed yarn (LFA) and consequently these first courses have less extensibility than the subsequent courses and those of the rest of the item, thus making the item more constraint at the edge of the waistband than on the rest of the item; it is a cause of discomfort for the wearer. Hence, in many cases one is compelled to have to cut this edge, thereby leading to an additional operation and a loss of time, thus also leading to an edge of a quality which is not necessarily irreproachable, possibly with the risk of the item running.